There were night flights even in the 1930s. There is ATC, radar. etc in the 1950s.

In the 1920s flights didnt operate at night but the DC3 and Boeing 247 are more than capable of night flying. The DC-3 was also called the DST "Douglas Sleeper Transport" when it entered service in 1936.

How do you think that TWA and Pan AM flew to Europe beginning in 1946? Overnight.